And finally tonight there are few families more bound by tradition than the british royals. The rules still taken very seriously. Even after diana defied them so what will will and kate, today's modern parents, do? Here's abc's nick watt. Reporter: Kate's already broken one rule, royal brides are supposed to be pregnant within a year of the wedding. The role of the princess mum is not easy. Diane tried to tear up the rule book. William, the first heir to the throne ever born in a hospital, not a palace. Diana, the first royal mum to dare complain of morning sickness. Also to fall asleep in public when her pregnancy was still a secret. Traditionally royals didn't actually see much of their kids. But not diana. She wants to be as present for her children as she possibly could. Reporter: There were some royal rules diana could not shake. Apparently william was induced, so the birth didn't interrupt prince charles' polo schedule. And the queen, not diana's own mum, was her first visitor. And the name, traditional, of course. Bookies' favorites right now for kate and william's first born are george and anne. Time has also ironed out the arcane and the downright barbaric. It was nearly 500 years ago that henry viii executed a wife who failed to produce a male heir. And it's been nearly 100 years since government officials had to be present at a royal birth to ensure the baby was not an imposter. The duty of the wife of the future king is to provide an heir and hopefully a spare. Reporter: And now it's time for the next generation. Nick watt, abc news, los angeles.

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